Bleachers, stands and riser assemblies are known in the prior art. U.S. Pat. Nos. 2,598,983 (to Ellis) and 3,2.29,430 (to Berg) disclose risers or staging steps that can be placed in a collapsed position for storage and an erected position for use. However, the disclosed risers do not include features for facilitating or enhancing their portability.
U.S. Pat. Nos. 2,859,488 (to Mackintosh), 3,747,706 (to Paine et al.), and 3,747,708 (to Wenger et al.), the latter two patents being assigned to the assignee of the present invention, relate to portable risers reconfigurable between a transport and storage position and an erect position. The risers have casters or wheels to facilitate their movement.
However, as noted in U.S. Pat. Nos. 3,974,894 and Re. 30,830 (both to Wenger et al. and both assigned to the assignee of the present invention), in each of the three patents noted in the preceding paragraph, it is necessary to turn the entire riser from a position for transport where the casters or wheels engage the floor to a position for being erected and supporting weight. The risers disclosed in the latter two Wenger patents do not require this turning, thereby simplifying their use. The latter two Wenger risers include a latch means to latch the riser in its erected position. The latch means include a hand operated wedging lock for forcing and holding apart a pair of latch rods. For folding the risers, the latch means must be unlocked and held by hand as the riser collapses.
There are at least several problems which have remained unaddressed by the above-noted prior art. When easy portability, including the capacity to be quickly and conveniently rearranged or moved, is a desired attribute for a portable riser, it would be advantageous if a riser unit, including the latching or locking mechanism, could be manipulated as quickly, easily, and conveniently as possible. While the latter two prior art patents disclose a latch means for locking the risers in their erect position, it would be more convenient and efficient if the latch or lock were operable with minimum effort by the person who is moving the risers.
The support frame and safety lock for insuring that a riser stays locked in its erected position during use should be structurally simple, strong, and able to be operated conveniently, thereby minimizing maintenance and the possibility of catastrophic failure. Additionally, the operation of the lock mechanism should be easy to understand and require a minimum amount of manipulation and effort to lock and unlock. It would be desirable that the operator does not have to assume an awkward, uncomfortable, bent-over position or reach beneath the riser to operate the lock by hand. It would also be desirable that the operator is required to manipulate only a single, foot-operated control at one end of the riser, thereby keeping the hands free for other tasks. It would be advantageous if no special tools were required for set up or knockdown of a riser unit.
Clearly, a strong, safe portable riser for entertainment or institutional use that is convenient to move from storage to the point of use, and easy to manipulate into various positions and configurations while in use, would be a decided improvement over the risers disclosed in the prior art.